Process and apparatus for catalytic oxidation



1,515,299 C. R. DOWNS ET AL PROCESS AND APPARATUS Fon cATALYTIc oxIbAfTIoN Filed Dac INVENTORY ATTORNEY raient Nev. u, 192e. l

CHARLES R. DOWNSAND CHARLES G. STUPP, OF CLIFFSIDE, NEW JERSEY, ASSIGNORS T0 THE BARRETT COMPANY, A CORPORATION OF NEW JERSEY. I

PaocEss AND APPTUSv ron. cATALY'rIc OXIDATION.

Application filed` December 7, 1918. Serial No. 265,777.I

To all whom t may concern:

Be it known that we, (l) CHARLES R. DOWNS and (2) CHARLES G. STUPP, citizens of the United States, residing at (1) Cliii'- side and (2) Cliii'side, in the counties of (l) Bergen and (2) Bergen and'States of (l) New Jersey and (2) New Jersey, have 1nvented certain new and useful Improvements in Processes and Apparatus for Catalytic Oxidation, of which the following is a specification.

This invention relates to a process of and an apparatus for removing the exothermic heat 'generated -by chemical reactions of compounds in the vapor dphase. The invention is especially adapte to the removal of heat from, the oxidation of organic compounds wherein the reaction is carriedout in 'the vapor phase in the presence of a catalyzer.V

It is-well known 'that many chemical reactionsv develop heat so that the temperature may sometimes rise so high as to be objec tionable and even injure the substances which it is desired to produce. This is especially true of lthe oxidation of organic.

compounds in the vapor phase by gaseous oxygen in the presence of a catalyzer when it is desired to produce partially oxidized products as distinct from products of comf A plete combustion. In 4all such oxidations it appears that there is a specific temperature `at which partial oxidation is initiated, for

` each compound in question, that there is a definite temperature range above this primary temperature wherein the products of artial oxidation are substantially stable 1n the presence of the vapor of the unreacted organic substance, excess oxygen and catalyst and'tlrat above this temperature there is a. point at which products of complete combustion are formed in undesirable amounts. When such oxidations take place a large proportion of the heat which is carried away by the eluent gases u but this4 is dependentupon the heat car ing ycapacity of the ltmg, Whllvel' 't e heat carrying capacity of the. eiiluent'ga'ses' is less in amount than the heat production of the reaction, this heat is stored up in the catalyst and must be removed by some other i means. This is often taken care of by al- 1 lowing said heat to be conducted by the catalytic mass to the walls of the reaction chamber and from thence radiating it to the atmosphere or to other cool gases. Apparatus of such design is applicable only to those reactions wherein the heat evolution is relatively small or else the linear heat travel by Aconduction must be greatly resuchlproductsthis would not be practicable.

and the purpose of the invention described 1n this application is to depictlan apparatus lwhereby this diiiiculty is solved in that chambers of any cross section may be used'.

Other forms of apparatus which havev u been used or suggested for controlling the heat of exothermic reactions of gaseous compounds lemploy the addition of live steam or cool reaction mixture injected into or near the reaction zone thereby remov- .ing the excess heat. When such means are used either an undesirable dilution of the reaction mixture takes place or there is a possibility of cooling the reacting gases below a temperature which is desirable forl aA proper reaction.

Still other forms of apparatusl make use of the alternate reaction and cooling zone system wherein the gases are allowed to alternately heat Aup and cool down. They,

however, do not embody su'iiicient control of the Vcatalyst tem erature exce t at the entering surface o the same. uch apparatuses depend only upon the heat carrying capacity of the eiuent gases and as noted above this is often insucient.

It has been the'object of the present ap- 4plicants to devise a form ofapparatus in which the disposition 'of the reaction zones and heat controlling meansV are such that heat removal takes place not only by convection` but more particularly' by radiation.

In practicing this invention the reaction mixture at the pro er temperature may be'A passed into a'regtrlcted'space-containing a catalyst whereupon the reaction begins and the` temperature rises. Before the reaction progresses too lfar and the temperature rises too high the mixture, in which the reaction has been only partially completed, is passed into a cooling space where its temperature is lowered and it is then passed into another similar space containin a catalyst where the reaction is continue with a consequent rise in temperature again. The mixture is again passed into a cooling space and so on until the reaction has developed as tar as desirable or feasible. lt has been found, however, that the percentage of the total reactionwhich it is possible to obtain in each catalyst chamber can be greatly inn creased by removing heat :trom the catalytic mass by radiation in addition to that by convection. ln this way the process is performed without seriously injuring the materials being treated or the products of the reaction and without materially slowing up the process.

The invention will be readily understood .from the accompanying drawings, and description in connection therewith, which illustrates a particular embodiment of the invention which has been 'found to work well in practice.

Figure l is a side view 'ot the apparatus shown partly in section.

iligure lll is an enlarged view ol one of the compartments shown in Figure l.

ln Figure l reference character l represents a chamber in which the reaction takes place. Leading into this chamber are the inlet members 2 and leading from it are the outlets 3. 'lhs reaction mixture entering the apparatus is heated in the members 2 to a temperature which is suitable for the inception of the reaction. This may be accomplished by heating the members 2 extei'nally by any means or by heating them internally by a. coil or otherwise. fin eX- ternal heating coil is shown at 2. The method of preheating the reaction mixture 1s unimportant provided it arrives in chamber l at substantially the lowest temperature at which it is proper to start the reaction. rlhe reaction chamber l is divided into a number of compartments 5. The compartments 5 contain a porous catalyst or a suitable porous vehicle such as ground or crushed pumice, asbestos, etc., carrying a catalyst/6 which is supportedl loyth'e pertorateblv shelves 7 or other suitable means through whlch the reaction gases may tree;

ly pass. llt is obvious that it the catalystvis by nature metallic and capable ol being woven into cloth or gauze, the shelves? are unnecessary as the catalyst may be suported from the wallsthe reaction chainer. Above the catalyst layer the compartments 5 contain pipe coils, grids, radiators, or other suitable cooling means 4c through nei/ease which independently re lated liquid or gaseous cooling Huids, ot er than those constituting the reaction mixture, may be internally circulated. Beyond the last compartment 5 is a nal cooling grid l. 'lhe outlets 3 lead to a condensing system of any suitable type not shown or to other suitable receptacles.

For purposes of more clearly describing the advantages of this apparatus Fig. lll is given in diagrammatic form in which is illustrated the catalytic mass. 'lhe line w-w represents a hypothetical portion or plane in the body ot the catalyst 6 in compartment 5 where heat is developed. Arrows b designate directions perpendicular to the plane a-a in which heat iiows from the plane by radiation. Arrow 0 pointing in the direction of vapor flow, designates 'the direction of heat flow by convection. Alt is evident that the proportion of heat flow by radiation in the direction of the arrows al. parallel to the plane Je-ai, becomes very small with`a catalytic layer ot any considerable dimensions transverse to the vapor flow. All removal of heat in the directions of the arrows al is, there-lore, disregarded in this application as being entirelyinsuticient, in a chamber of ordinary size to control the reaction.. Catalyticlayers havding lengths and breadths each. more than titty times their depths have been `lfound to operate satisfactorily and to be easily controlled when maleic acid is being produced from benzene. this :tlow oi" heat from the catalytic mass both by convection and radiation in the manner described above is decidedly beneicial and that thereby regulation ot the temperature ot the catalyst may be very closely controlled.' lt is also apparent that to obtain the greatest eciency oit catalyst temperature control the grids both below and above the catalyst layer must be very close to the same.a

llt is also to be noted that there is no direct contact between the catalyst andthe cooling grids or heat extracting means fl, such contact would be detrimental where it is necessary to use a cooling fluid whose L temperature must be below the proper reaction temperature lin the catalytic Zone. Physical contact under such conditions would result in uneven cooling oit the catalyst'by conduction, with certain particles of l it so chilled, as to interfere with their tune* `tion or lessen their etiiciency in the processy The operation will be described specit ically in connection with the treatment ot benzene to form maleic acid by oxidation in the presence oit a catalyst such as vanadiu'm oxide, though it is to be understood that the invention is not to be restricted to these particular materials as the process can be practiced 'with many other materials lso compartment 5 and then comes into Contact" with the catalyst 6, such as vanadium oxide. and the reaction by which maleic acid is formed, begins. The temperature rises .rap-

j idly because of the exothermic action and if it were not properly and carefully controlled it would rise so high that the prodemerge from the catalyst zones is insufficienty and that a large proportion of the heat developed in these zones is radiated ,to the coo-ling means 4 above and below the saine and that this property is a vital advantage of our apparatus. The direction of reaction mixture flow throughout the whole system is indicated by the arrows 8. The number and depth of the reaction, and cooling zones will be selected to suit the materials being treated. With benzene to form. maleic acid as above outlined, the depth and the concentration of the catalyzer, the velocity of the reaction mixture, the relation of oxygen to benzene and the presence or absence of diluent gases .all share in determining the low'-'and high temperatures allowable in the catalytic mass. There is, however, a, certain range of temperature between that at which' maleic acid is formed and that at which it is further oxidized largely to CO2 and H2O.

lCertain combinations of the above variables allow this temperaturerange to be 50o C., that is. the reaction mixture must enter, the catalytic mass not below 400. C., and leave not above 450 C. Other combinations may. 4prescribe considerably different temperature conditions.

Fixed temperature limits for proper op-l eration are also needed for practically all partial oxidations of Ior anic substances in the vapor phasewith w ich the applicants i vare familiar. This is also true of many inorganic Oxidations in the vapor'4 phase except that in these cases an undesirable rise iu temperature results in the dissociation of the desiredl products rather than in the formation o higher oxidation products. The apparatus as described in this application has been designed to properly control the catalyst temperature for 'such reactions so that the accelerating effect of exothermic heat formation may be retarded, to prevent the complete oxidation of organic compounds on the one hand or to prevent the undesirable dissociation of inorganic oxidation products on the other.

In addition to the partial oxidation of benzene, as above described this apparatus may be used to provide the proper reaction temperature for the partial oxidation of many other compounds such as naphthalene, toluene, anthracene, phenanthrene, aniline, ortho cresol, phenol, xylene, cresol, methyl alcohol and ethyl alcohol, both of which are alifatic alcohols, alifatic alcohols, ethylene, acetylene, ammonia, SOQ, etc., when these are in the vapor phase and mixed with oxygen containing gases as oxidizing agents.

Itis obvious that in all cases the particular temperature limits between which the catalytic zone is maintained will be dependent upon the particular mixture which is being treated. The dcsideratum to be attained is that the temperature should not be so lowy that the reactionv will not be produced nor so high that the products will be decomposed to any very great extent. The temperature in the. successive reaction chambers may be made to increase or decreaseprogressively, if desired, lby extracting less or more heat by the ,cooling means than is evolved in the reaction zones. That is to say, as diluent gases, for example C02 or other 'by-products increase in amount with each reaction zone it may be advisable to allow the temperature of the successive catalytic zones to increase progressively.

It is not our intention that this apparatus be restricted to the use of vanadium oxide, as a catalyst, but any catalyst that will accomplish .the desired result maybe employed. n

Claims:

l. The process oit producing maleic acidv which comprises raising thel vapor of benzene mixed with an oxygen containing gas to a temperature of approximately 400 0., passing the mixture into contact with `vanadium oxide as a catalyst, permitting the temperature lto rise about 50 C. and then passing said mixture into contact with a cooling surface. l

2. The processA of producing maleic acid which com rises raising the. vapor of benzene mixe with an oxygen containing gas to a temperature of about 400l C. at which i 'the benzene ring will be split and maleic acid' will Abe formed. in 'theA presence of vanadium oxide as a catalyst, passing said heated mixture into contact with the catalyst and permitting the temperatureto rise, and

' removing said mixture from contact with zene vapor and-an oxygen containing gas.

into Contact with vanadium oxide as a catalyst a plurality of times in succession at a temperature of about 400 mote reaction and cooling said mixture to a temperature of approximately 400o C. to proramene while in transit between successive contacts with the catalyst.

4. rllhe process of producing maleic acid which cornprisespassing benzene vapor and an oxygen containing gas through a plural.

ity of thin layers of' vanadium oxide heatd .and maintaining the temperature Withii an approximate range of 50 C. by removing heat from between said layers of catalyst.

ln testimony whereof We aix our signatures'.

*CMRLES R. DWNS. @Hannes e. entre. 

